Circuit breaker



Dec. 1, 1931. J. E. MCGEE CIRCUIT BREAKER Filed July 14, 1928 INVENTOR John E.- McGee.

A'II'TORNEY Patented Dec. 1, 1931 UNITED STATES PATENTY OFFICE.

JOHN E. MCGEE, OF WILKINSIBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA cmcnrr BREAKER Application filed my 14, 1928. Seria1 No. 292,729.

Myinvention relates to circuit breakers and particularly to circuit breakers of the air-break type wherein the arc incident to the operation of the contacts moves between a plurality of metal plates or grids, and is broken u into a series of arcs that are rapidly deionized and extinguished as it travels between thegrids.

Circuit breakers of this type have been provided with a plurality of sheet-metal grids, and means have been'provided for causing the are between the grids to move at high velocityin a circular path in order to prevent burning of the grids, the velocity of the arc being such that it does not occupy a position on the grid for sufficient time to volatilize the metal thereof. Consequently, no injury is done to the grids which may be used for repeated operation of the circuit breaker.

A circuit breaker having the above-noted characteristics is disclosed in the co-pending application of Francis C. Todd-Circuit interrupters, Serial No. 292,824, filed July 14, 1928, and assigned to the Westinghouse Electric & Manufacturing Company. The grids disclosed in the above-noted application are provided with tangential slots radiating from an opening in the center of the grids. When an arc is moved in the space between the grids, it follows the direction of the slots that lead toward the central opening which is covered with an insulating bushing. When the arc reaches a position near the central opening, it has a tendency to revolve thereabout, due to the magnetic field induced by the current flowing in the iron grids reacting upon the electric currentof the arc.

While the slots in the grids tendto maintain the arc in a circular orbit near the center of the plates, under certain operating conditions, the arc moves dangerously near the edges of the grids.

Before the slots were embodied in the grids V to determine the path of thearc, grids without slots were used, but it was found necessary to confine the are by filling the space between the grids, near the marginal edges thereof, with insulation. This closure of the space between the plates, adjacent to the edges thereof, 'wasnot satisfactory for heavy duty or frequent service because of insufii cient ventilation and consequent overheating of the grids, accompanied by high pressures between the grids,'which frequently caused failure of the circuit breaker.

An object of my invention is to provide a circuit breaker of the type disclosed in the above-noted co-pending application wherein means are provided for so influencing the are that it is attracted toward the center of the grids and so confined that it moves in a definite circular orbit, a safe distance within the boundaries of the grids. A further object of my invention is to provide a circuit breaker having the above-noted characteristics, wherein a conductor extends through the central openings in the grids and which is so connected in series with the arc that the current flows through the conductor in the same direction thatit flows through the arc stream. The conductor exertsan' at tractive force upon the arc and tends to draw it towardthe center of the grids as it revolves at a high velocity about the central opening. V

A further object of my invention is to provide a circuit breaker having the abovenoted characteristics wherein a simple and inexpensivemeans is provided for fixing the orbit of the are near the central zone of the grids. v

These and other objects that will be made apparent throughout the further description of my invention are attained by means of. the apparatus hereinafter described, and illustrated in the accompanying" drawings wherein: i

Figure 1 is a side elevation of a circuit breaker embodying features of myinvention and showing the grid structure in section;

Fig. 2 is a plan view of the grid used in the circuit breaker shown in Fig. 1; and

Fig. 3 is a side elevationof the grid shown in Fig. 2.

Referring to the drawings, the circuitbreaker apparatus, such as is disclosed in the above-noted co-pending application, comprises an insulating base 4, upon which is mounted a stationary contact member 5 and i i to a movable switch arm 7, pivotally mounted upon a bracket 8, that is secured to the insulating base l.

The switch arm 7 is provided with an armature 9 that cooperates with the pole pieces 11 and 12 of an electromagnetic coil 13 which is connected to a control circuit that may be controlled by a current-responsive relay or be manually operated, as desired. When the coil is energized, the contact member 6 is held in engagement with the contact member 5 and, when the coil is deenergized, a spring 14, connecting an extension 15 of the switch arm 7 and a bracket 16 mounted on the base 4, causes the switch arm to move to open position with a snap action.

The arc-extinguishing device comprises a plurality of sheet-iron grids 17, of U-shape, that are secured in assembled spaced rela tion by means of bolts 18 and a. bolt 19, that are surrounded by insulating bushings 21 and 22, respectively, and which are insulated from the grids. The grids 17 are disposed bet-ween two spaced sheet-iron plates 23 and 24, and the grids 17 and plates 23 and 24. are separated from one another by insulating washers 25 surrounding the bushing 21, and insulating washers 26 surrounding the bushing 22. The plate 23 is conductively connected to the contact member 5, and the plate, 24 is conductively connected to the switch arm 7 by means of a conductor 27. The switch arm 7 is connected to a feed conductor terminal 28 mounted on the base 4 by means of a flexible conductor 29.

The grids 17. are provided with spiral slots 31 which radiate from the central opening 32 in the grids, as shown in Fig 2.

WVhen an arc is drawn between the contacts 5 and 6, it immediately engages the lower end of the grid 17 and moves upward- ]y between the grids until it engages one of the slots. The are has a tendency to follow the slot toward the center opening in the grid, and movement from the center of the grid is opposed by its engagement with. additional slots which again direct it toward the center, adjacent to the washer 26 surrounding the bolt 19 about which the are tends to rotate.

The construction so far described is disclosed in the above-noted co-pending application, and no claim is made to the structure heretofore described except in combination with the invention about to be described. It has been found that, under certain operating conditions, the arc moves dangerously near the edges of the grids, and it is an ob ject of my invention to provide a simple means for insuring that the arc shall be confined to a zone near the central portion of the grids and that it shall be caused to move in a substantially definite circular orbit about the central openings in the grids, exteriorly of the insulating washers 26.

I have, therefore, provided the central bolt 19 of conductive material, and have connected it in the circuit through the circuit breaker, contacts 5 and 6 and the are subsequently drawn and moved into the grids, in such manner that the current flows through the central conductor bolt 19 in the same direction that current flows through the are drawn be tween the grids 17 and the end plates 23 and 24. The bolt 19 extends through the base 4 and is provided with a feed-terminal member 33. A conductor 34 connects the opposite end of the conductor bolt 19 to the contact member 5. The current flows, through the circuit breaker, when the contacts are in closed position, from the said terminal 33, through conductor bolt 19, conductor 34%, contact members 5 and 6, circuit-breaker arm 7 and flexible conductor 29, to the feed-conductor terminal 28.

the arc is moved between the grids and the plates 23 and 24, the current flows from the plate 23, through the arc to the right-hand grid 17, the bent end of the grid, an are between the right-hand grid and the central grid, the bent end of the central grid, an are connecting the central grid with the left-hand grid 17, an are between the outer grid and the plate 24:, the conductor 27 and flexible conductor 29, to the conductor terminal 2 Since the current passes through the conductor bolt 19 in the same direction that it passes through the arcs, the arc and the conductor bolt 19 being of the same polarity, at any instant, causes the are to be attracted toward the conductor bolt 19, which prevents the are from moving outwardly toward the edges of the grid as it revolves about the central portion of the grid. The conductor bolt 19 also assists in the initial movement of the are into the grids.

It will be understood that any number of grids 17 may be used, depending upon the voltage of the circuit to be interrupted, it being the usual practice toprovide a grid for each 100 root mean square volts. It has been found that where approximately the above are voltage for each grid is not exceeded, the arc is extinguished and prevented from reforming within the first half cycle of an alternating current.

While I have illustrated but one embodiment of my invention, it will be apparent to those skilled in the art that various changes, modifications, substitutions, additions and omissions may be made in the apparatus illustrated without departing from the spirit and scope of my invention, as set forth in the appended claims.

I claim as my invention:

1. The combination with a circuit breaker having a plurality of arc-quenching plates between which an arc is sectionalized and caused to move, of a fixed conductor extend- I Then the circuit breaker has opened, and

a plurality of arc-quenching conductive plates which serve as are terminals and between which an arc is sectionahzed and caused to move, of means including a current conductor disposed parallel with the arcs for creating a field near the center of the plates that exerts an attractive force upon the arcs.

3. The combination with a circuit breaker having separable are drawing cont-acts and a plurality of arc-quenching plates between which the are from the contacts is sectionalized and caused to move, and which are provided with means for directing the arcs toward the center of the plates and which coopcrate in causing the arcs to move in a circular path within the space between the plates, of current-responsive means near the center of the plates for stabilizing the arcs and preventing their movement'toward the edges of the plates.

at. In combination with a circuit breaker having separablearc drawing contacts a pair of arc-quenching conductive plates which serve as are terminals and between which the are from the contacts is sectiona-lized and caused to move in a circular path, of electromagnetic means near the center of the revolution of the arcs for influencing the arcs to prevent their movement toward the edges of the plates.

5. The combination with. a circuit breaker having separable arc-drawing contacts and pair of arc-quenching conductive plates which serve as are terminals and between which the are from the contacts 1s caused to move, of electromagnetic means near the center of the plates for influencing the arc to confine its orbit near the center of the plates.

6. A circuit breaker comprising a pair of relatively movable contact members between which an arc is drawn, a stack of spaced metal (lo-ionizing plates into which the arc is moved, the plates serving as are terminals dividing the are into a plurality of seriesrelated sect-ions between which the arc moves, and a current conductor extending through the stack and so connected in series relation to the said contact members that the current flow therethrough is in the same direction as that through the said are sections for creatinga magnetic field tending to attract the arcs toward the conductor.

7 A circuit breaker comprising a pair of relatively movable contact members between which an arc is drawn, a stack of spaced metal de-ionizing plates into which the arc is moved,

the plates serving as are terminals dividing the are into a plurality of series-related sections between which the arc moves, the said plates having means forcausing the arc to move in a circular orbit about a point interior of the stack and a-current conductor extending through the stack and so connected in series relation to theisai'd contact members that the current flow therethrough is in the same direction as that through the said are sections "for creating a magnetic field tending to attract the arcs toward the conductorr v 8. "A circuit breaker comprising a pair of relativelymovable contact members between which an arcisdrawn, a stack of spaced metal d'c-ion'izing plates disposed adjacent the contact members for receiving the are drawn therebetween and for sectionalizing the are into a plurality of series-related sections that are moved between the plates toward the interior of the stack, and a current conductor extending through the stack, and insulated from the plates thereof and connected in the circuit controlled by the contact members so that current flows through the arc sections and the said conductor inthe same direction.

- having continuous open passages extending therebetween, and between which an arc is sectionalized and caused to move, of a fixed conductor extending through the plates and insulated therefrom and so connected in the circuit of the arcs that current is conducted therethrough in the same direction that it is flowing through the arcsf 10. The combination with a circuit breaker having separable are drawing contacts and a plurality of arc-quenching conductive plates which serve asarc terminals and between which an arc is sectionali'zed and caused to move, of means including a current conductor disposed parallel with the arcs'for creating a field near the center of the plates that exerts an attractive force upon the arcs and continuous open spaces between 11, The combination with a circuit breaker having separable are drawing contacts and a pair of arc-quenching conductive plates which serve as are terminals and between which the are from the contacts is caused to move, of electromagnetic means near the center of the plates for influencing the arc to confine its orbit near the center of the plates and open spaces between said plates from a point adjacent said are drawing con tacts to the'opposite side of said plates.

12. A circuit breaker comprising a pair of relatively movable contact members between which an arc is drawn, a stack of metal deionizing plates having open spaces therebetween extending entirely through said stack a plurality of series-related sections between which the arc moves, means for causing the arc to move in a circular orbit about a point interior of the stack and a current conductor extending through the stack and so connected in series relation to the said contact members that the current flow therethrough is in the same direction as that through the said are sections for creating a magnetic field tending to attract the arcs to- Ward the conductor.

In testimony whereof, I have hereunto subscribed my name this lOth day of Jul 1928.

JOHN E. Mo EE. 

